96 infrequent stalling

I just bought a 96 blazer 4 wheel drive 4 door LS. The truck has 82k miles. The previous owner put a new engine in it. The new engine has about 500 miles on it. I put all the miles on it. The engine did not include everything on the top (ie fuel system). When I am driving it some times it begins loosing engine power and it begins to slow down despite me adding gas. Since I always run with the headlights on the power comes back when I turn the lights off. I can immediately turn the lights back on an it will run fine for another 50-75 miles.

PS. I hate the buzzing of the fuel pump!!! The prevous owner put a new aftermarket fuel pump in.

continuation of my original post.

The air bag light also comes on about 5 seconds after starting and stays on. There are no error codes.

Also, the check engine soon light comes on after about 20 miles after reseting the codes, all the O2 sensors begin giving an error.

Your alternator is weak or you have a major short in the system.

Also, the whining fuel pump is completely normal.

Your alternator is weak or you have a major short in the system.

Also, the whining fuel pump is completely normal.

The short is a great suggestion. Is there a forum or a website that has a nice check list of tracking down a short?

Hold on, check your volt gauge on your dash and tell us where it is reading when this problem occurs.

Hold on, check your volt gauge on your dash and tell us where it is reading when this problem occurs.

I maintains a constant level just below 14. Is this good or bad?

put your AC on and your fan on max with your headlights on high beam and see if it starts to fall.

Yes, it dropped down to about 11-12 volts with the with the ac on high. Turning the headlights on did not effect the volts much.

One more thing. Something else is weird. When I am accelerating or idling, it is fine. But when I have my foot barely on the gas to maintain speed, such as the highway, I feel the engine surging. I do not have a tach, but I would guess it osilates at about +/- 100 rpm.

Furthermore, I had the guys at the autostore check the errors again. They said both O2 sensors were bad (again). also it said that there were 2 errors for "fuel/air" mixture. I then replaced the O2 sensors, and again. After about 20 miles. The Check engine light comes on. I suppose it is the O2 sensors. And they are NEW.

You have a alternator that is weakening and is about to pop.

That or your battery is shot.

Go get both load tested.